On Sat, May 19, 2018 at 06:22:35PM +0300, Julian Anastasov wrote:
> syzkaller reports for buffer overflow for interface name
> when starting sync daemons [1]
>
> What we do is that we copy user structure into larger stack
> buffer but later we search NUL past the stack buffer.
> The same happens for sched_name when adding/editing virtual server.
>
> We are restricted by IP_VS_SCHEDNAME_MAXLEN and IP_VS_IFNAME_MAXLEN
> being used as size in include/uapi/linux/ip_vs.h, so they
> include the space for NUL.
>
> As using strlcpy is wrong for unsafe source, replace it with
> strscpy and add checks to return EINVAL if source string is not
> NUL-terminated. The incomplete strlcpy fix comes from 2.6.13.
>
> For the netlink interface reduce the len parameter for
> IPVS_DAEMON_ATTR_MCAST_IFN and IPVS_SVC_ATTR_SCHED_NAME,
> so that we get proper EINVAL.
>
> [1]
> kernel BUG at lib/string.c:1052!
> invalid opcode: 0000 [#1] SMP KASAN
> Dumping ftrace buffer:
> (ftrace buffer empty)
> Modules linked in:
> CPU: 1 PID: 373 Comm: syz-executor936 Not tainted 4.17.0-rc4+ #45
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> RIP: 0010:fortify_panic+0x13/0x20 lib/string.c:1051
> RSP: 0018:ffff8801c976f800 EFLAGS: 00010282
> RAX: 0000000000000022 RBX: 0000000000000040 RCX: 0000000000000000
> RDX: 0000000000000022 RSI: ffffffff8160f6f1 RDI: ffffed00392edef6
> RBP: ffff8801c976f800 R08: ffff8801cf4c62c0 R09: ffffed003b5e4fb0
> R10: ffffed003b5e4fb0 R11: ffff8801daf27d87 R12: ffff8801c976fa20
> R13: ffff8801c976fae4 R14: ffff8801c976fae0 R15: 000000000000048b
> FS: 00007fd99f75e700(0000) GS:ffff8801daf00000(0000)
> knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00000000200001c0 CR3: 00000001d6843000 CR4: 00000000001406e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
> strlen include/linux/string.h:270 [inline]
> strlcpy include/linux/string.h:293 [inline]
> do_ip_vs_set_ctl+0x31c/0x1d00 net/netfilter/ipvs/ip_vs_ctl.c:2388
> nf_sockopt net/netfilter/nf_sockopt.c:106 [inline]
> nf_setsockopt+0x7d/0xd0 net/netfilter/nf_sockopt.c:115
> ip_setsockopt+0xd8/0xf0 net/ipv4/ip_sockglue.c:1253
> udp_setsockopt+0x62/0xa0 net/ipv4/udp.c:2487
> ipv6_setsockopt+0x149/0x170 net/ipv6/ipv6_sockglue.c:917
> tcp_setsockopt+0x93/0xe0 net/ipv4/tcp.c:3057
> sock_common_setsockopt+0x9a/0xe0 net/core/sock.c:3046
> __sys_setsockopt+0x1bd/0x390 net/socket.c:1903
> __do_sys_setsockopt net/socket.c:1914 [inline]
> __se_sys_setsockopt net/socket.c:1911 [inline]
> __x64_sys_setsockopt+0xbe/0x150 net/socket.c:1911
> do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
> entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x447369
> RSP: 002b:00007fd99f75dda8 EFLAGS: 00000246 ORIG_RAX: 0000000000000036
> RAX: ffffffffffffffda RBX: 00000000006e39e4 RCX: 0000000000447369
> RDX: 000000000000048b RSI: 0000000000000000 RDI: 0000000000000003
> RBP: 0000000000000000 R08: 0000000000000018 R09: 0000000000000000
> R10: 00000000200001c0 R11: 0000000000000246 R12: 00000000006e39e0
> R13: 75a1ff93f0896195 R14: 6f745f3168746576 R15: 0000000000000001
> Code: 08 5b 41 5c 41 5d 41 5e 41 5f 5d c3 0f 0b 48 89 df e8 d2 8f 48 fa eb
> de 55 48 89 fe 48 c7 c7 60 65 64 88 48 89 e5 e8 91 dd f3 f9 <0f> 0b 90 90
> 90 90 90 90 90 90 90 90 90 55 48 89 e5 41 57 41 56
> RIP: fortify_panic+0x13/0x20 lib/string.c:1051 RSP: ffff8801c976f800
>
> Reported-and-tested-by: syzbot+aac887f77319868646df@xxxxxxxxxxxxxxxxxxxxxxxxx
> Fixes: e4ff67513096 ("ipvs: add sync_maxlen parameter for the sync daemon")
> Fixes: 4da62fc70d7c ("[IPVS]: Fix for overflows")
> Signed-off-by: Julian Anastasov <ja@xxxxxx>
Acked-by: Simon Horman <horms+renesas@xxxxxxxxxxxx>
> ---
> net/netfilter/ipvs/ip_vs_ctl.c | 21 +++++++++++++++------
> 1 file changed, 15 insertions(+), 6 deletions(-)
>
> diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c
> index f360988..3ecca06 100644
> --- a/net/netfilter/ipvs/ip_vs_ctl.c
> +++ b/net/netfilter/ipvs/ip_vs_ctl.c
> @@ -2381,8 +2381,10 @@ do_ip_vs_set_ctl(struct sock *sk, int cmd, void __user *user, unsigned int len)
> struct ipvs_sync_daemon_cfg cfg;
>
> memset(&cfg, 0, sizeof(cfg));
> - strlcpy(cfg.mcast_ifn, dm->mcast_ifn,
> - sizeof(cfg.mcast_ifn));
> + ret = -EINVAL;
> + if (strscpy(cfg.mcast_ifn, dm->mcast_ifn,
> + sizeof(cfg.mcast_ifn)) <= 0)
> + goto out_dec;
> cfg.syncid = dm->syncid;
> ret = start_sync_thread(ipvs, &cfg, dm->state);
> } else {
> @@ -2420,12 +2422,19 @@ do_ip_vs_set_ctl(struct sock *sk, int cmd, void __user *user, unsigned int len)
> }
> }
>
> + if ((cmd == IP_VS_SO_SET_ADD || cmd == IP_VS_SO_SET_EDIT) &&
> + strnlen(usvc.sched_name, IP_VS_SCHEDNAME_MAXLEN) ==
> + IP_VS_SCHEDNAME_MAXLEN) {
> + ret = -EINVAL;
> + goto out_unlock;
> + }
> +
> /* Check for valid protocol: TCP or UDP or SCTP, even for fwmark!=0 */
> if (usvc.protocol != IPPROTO_TCP && usvc.protocol != IPPROTO_UDP &&
> usvc.protocol != IPPROTO_SCTP) {
> - pr_err("set_ctl: invalid protocol: %d %pI4:%d %s\n",
> + pr_err("set_ctl: invalid protocol: %d %pI4:%d\n",
> usvc.protocol, &usvc.addr.ip,
> - ntohs(usvc.port), usvc.sched_name);
> + ntohs(usvc.port));
> ret = -EFAULT;
> goto out_unlock;
> }
> @@ -2847,7 +2856,7 @@ static const struct nla_policy ip_vs_cmd_policy[IPVS_CMD_ATTR_MAX + 1] = {
> static const struct nla_policy ip_vs_daemon_policy[IPVS_DAEMON_ATTR_MAX + 1] = {
> [IPVS_DAEMON_ATTR_STATE] = { .type = NLA_U32 },
> [IPVS_DAEMON_ATTR_MCAST_IFN] = { .type = NLA_NUL_STRING,
> - .len = IP_VS_IFNAME_MAXLEN },
> + .len = IP_VS_IFNAME_MAXLEN - 1 },
> [IPVS_DAEMON_ATTR_SYNC_ID] = { .type = NLA_U32 },
> [IPVS_DAEMON_ATTR_SYNC_MAXLEN] = { .type = NLA_U16 },
> [IPVS_DAEMON_ATTR_MCAST_GROUP] = { .type = NLA_U32 },
> @@ -2865,7 +2874,7 @@ static const struct nla_policy ip_vs_svc_policy[IPVS_SVC_ATTR_MAX + 1] = {
> [IPVS_SVC_ATTR_PORT] = { .type = NLA_U16 },
> [IPVS_SVC_ATTR_FWMARK] = { .type = NLA_U32 },
> [IPVS_SVC_ATTR_SCHED_NAME] = { .type = NLA_NUL_STRING,
> - .len = IP_VS_SCHEDNAME_MAXLEN },
> + .len = IP_VS_SCHEDNAME_MAXLEN - 1 },
> [IPVS_SVC_ATTR_PE_NAME] = { .type = NLA_NUL_STRING,
> .len = IP_VS_PENAME_MAXLEN },
> [IPVS_SVC_ATTR_FLAGS] = { .type = NLA_BINARY,
> --
> 2.9.5
>
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